From: Scott Mayhew <smayhew@redhat.com>
Date: Fri, 20 Jun 2014 12:44:42 +0000 (-0400)
Subject: nfs: Fix cache_validity check in nfs_write_pageuptodate()
X-Git-Tag: omap-for-v3.16/fixes-rc4~54^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18dd78c427513fb0f89365138be66e6ee8700d1b;p=pandora-kernel.git

nfs: Fix cache_validity check in nfs_write_pageuptodate()

NFS_INO_INVALID_DATA cannot be ignored, even if we have a delegation.

We're still having some problems with data corruption when multiple
clients are appending to a file and those clients are being granted
write delegations on open.

To reproduce:

Client A:
vi /mnt/`hostname -s`
while :; do echo "XXXXXXXXXXXXXXX" >>/mnt/file; sleep $(( $RANDOM % 5 )); done

Client B:
vi /mnt/`hostname -s`
while :; do echo "YYYYYYYYYYYYYYY" >>/mnt/file; sleep $(( $RANDOM % 5 )); done

What's happening is that in nfs_update_inode() we're recognizing that
the file size has changed and we're setting NFS_INO_INVALID_DATA
accordingly, but then we ignore the cache_validity flags in
nfs_write_pageuptodate() because we have a delegation.  As a result,
in nfs_updatepage() we're extending the write to cover the full page
even though we've not read in the data to begin with.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Cc: <stable@vger.kernel.org> # v3.11+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
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